Robotic mesh structure generation for concrete formwork and reinforcement

ABSTRACT

In one aspect the invention relates to a mobile robotic end-effector tool for generating a mesh structure for use in reinforced concrete building systems. The tool comprises: —at least one robotic end-effector (EE), being movable in six degrees of freedom for applying an endless secondary mesh structure (2 ms) to the provided primary mesh structure (1 ms) continuously by roll spot welding, —wherein the at least one robotic end-effector (EE) further comprises: —a welding unit (W), in particular a resistance welding unit, configured for welding the secondary mesh structure (2 ms) to the primary mesh structure (1 ms) at predefined connection positions to generate cross-wire connections; —contact force sensors, configured for measuring the contact force of the robotic end-effector (EE), being applied to the primary mesh structure (1 ms) during rolling over the primary mesh structure (1 ms); —a processor (P) for closed loop control of the at least one robotic end-effector (EE) by means of control signals, wherein the control signals are generated at least in part in response to the measured contact force.

The present invention is in the field of constructional engineering andin particular relates to a method for generating a mesh structure, whichmay be used for reinforcing concrete structures in buildingconstruction. Further, the invention refers to a robotic end-effectortool and a computer program.

In constructional engineering and/or automated manufacturing, meshstructures are used for a variety of different purposes andapplications. In particular, metal meshes may be used as a reinforcementstructure for being later filled with concrete for building walls and/orceilings.

On the one hand, in today's constructional engineering systems, therequirements for further automation of the building process areincreasing steadily for being able to save costs. On the other hand,building structures are getting more and more complex, and thusrequiring three-dimensional mesh structures in complex shapes and formswith curvatures and a variety of concave and convex mesh structuresections.

In state-of-the-art it is known to use robotic systems for manufacturingreinforcement structures for building systems. For example, WO2017/153559 A1 shows such an automated robotic set up for producingmetal meshes. Although this system provides the option to manufacturemeshes by means of a mobile digitally controlled robot, the system stillhas drawbacks with respect to performance and with respect to the fieldof application. The field of application is limited, because thesecondary mesh structure (discrete metal wires or rebars), which is tobe applied robotically on a primary mesh structure is restricted todiscrete elements in a defined length This limits the system forstructural applications since the reinforcement is only continuous inone direction.

An approach for automatically assembling planar rebar mats is shown inUS 2018/0333764 A1. Two-dimensional rebar mats are placed on a supporttable for being processed by several articulated arm robots. However,with this system, it is not possible to manufacture more complex meshstructures with a plurality of different types of curvatures.

It is therefore an object of the present invention to provide a solutionfor generating mesh structures being usable in reinforced concreteconstruction, which generally requires appropriate and sufficientreinforcement structures for being able to provide load and/or forcetransfer. Moreover, the manufacturing process for these mesh structuresshould be further automated and performance shall be improved.

This object is solved by the appended independent claims, in particularby a partially computer implemented method for generating a meshstructure, a robotic end-effector tool and a computer program.

Further advantages, advantageous aspects, features and/or embodimentsare mentioned in the dependent claims.

Further, it is to be pointed out that software typically is modular innature. Thus, a specifically implemented feature which is mentioned incombination with a certain embodiment may also be combined with otherfeatures, even when mentioned in other embodiments. Accordingly, anyfeature may be combined with at least any other feature, which isclaimed and/or described in this application, even when in anothercontext.

In the following, the invention is described with respect to the claimedmethod. Features, advantages or alternative embodiments mentioned withrespect to the method can also be assigned, transferred or, applied tothe other claimed or described subject matters, like the apparatus typeclaims (e.g., directed on the tool or the computer program or a computerprogram product) and vice versa. In other words, the subject matter ofthe robotic end-effector tool can be improved or further developed withfeatures described or claimed in the context of the method and viceversa. In this case, the functional features of the method are embodiedby structural units of the system, configured to dedicatedly executethis function and vice versa, respectively. Generally, in computerscience at least from a computational point of view, a softwareimplementation and a corresponding hardware implementation areequivalent, at least from a computability perspective. Thus, forexample, a method step for “storing” data may be performed with a“storage unit” and respective instructions to write data into thestorage.

For avoiding redundancy, these embodiments are not reiterated orexplicitly described again for the apparatus, because they have beendescribed already in relation to the method.

Wherever not already described explicitly, individual embodiments, ortheir individual aspects and features, described herein can be combinedor exchanged with one another, even when mentioned in other embodiments,without limiting or widening the scope of the described invention,whenever such a combination or exchange is meaningful and in the senseof this invention. Accordingly, any feature may be combined with atleast one other feature, which is claimed and/or described in thisapplication.

The order, according to which the steps of the method of the presentinvention are described in the present specification, does notnecessarily reflect the chronological order, according to which saidsteps are carried out.

According to a first object, the present invention refers to a methodfor generating a mesh structure for use in architecture, engineeringand/or construction, in particular for use in reinforcement systems, andmore particular for use in reinforced concrete structures. The methodconsists at least of the following method steps:

-   -   Providing a primary mesh structure, which may comprise a variety        of wires with different curvatures in different extensions        and/or with different radii,    -   Using a robotic end-effector tool with at least one        end-effector, wherein the (at least one) end-effector is movable        (preferably on an articulated arm) in six degrees of freedom for        applying a continuous or endless secondary mesh structure (e.g.,        a continuous metal wire strand) to the provided primary mesh        structure—in particular continuously—by roll spot welding. In a        preferred embodiment, the step of using the robotic end-effector        tool may only be initiated, after having received an initiation        signal (which, for example, may be provided on a user interface        by a human operator) for providing an additional verification        step.    -   and during rolling (the at least one end-effector) over the        primary mesh structure for roll spot welding:        -   instructing a welding unit, in particular a resistance            welding unit, to initiate a welding process within a            sequence of interrupted welding processes for welding the            secondary mesh structure to the primary mesh structure at            pre-defined connection positions to generate cross weldings;        -   instructing a set of sensors to measure—preferably            continuously—a contact force of the robotic end-effector,            being applied to the primary mesh structure during rolling            over the primary mesh structure;        -   (in particular closed-loop) controlling the robotic            end-effector in real-time by means of control signals,            generated by a processor, wherein the control signals are            generated at least in part in response to the measured            contact force and in particular to reach a desired or            targeted contact force (required to reach a sufficient            welding connection).

The solution according to the present invention provides a number ofadvantages. By using the robotic end-effector tool, which is configuredand engineered for roll spot welding and for welding the secondary meshstructure continuously, it is possible to use this method and system forreinforced concrete construction. In particular, mesh structures whichare to be used for reinforcement of concrete have to comply with a setof requirements. One of these requirements is the transfer of the loadand forces for the later building structure from a statical point ofview. For example, if a curved wall needs to be manufactured withdifferent radii, mesh portions with small radius of curvature (i.e.,highly curved structure) need a different mesh density (in particular ahigher density) than mesh portions with a big radius of curvature (i.e.,less curved structure) and vice versa.

Further, for being able to provide a sufficient load transfer, theprimary mesh structure should be reinforced with the secondary meshstructure in a continuous format. “Continuous format” means that thesecondary mesh structure, for example a metal wire or a strand inanother material, is welded to the primary mesh structure overpreferably the whole length or over the whole width of the primarystructure. In case the secondary mesh structure is to be appliedhorizontally, the secondary mesh structure preferably covers the wholewidth of the primary structure and extends from right to left (or viceversa). In this case (horizontal application of the second meshstructure), usually, the primary mesh structure comprises verticalelements or strands which serve as the basis for welding the secondarymesh structure. The secondary mesh structure is welded onto the primarymesh structure in a “continuous format”, meaning that the secondary meshstructure wire is welded at a plurality of cross-wire connections, andin particular at more than two cross-wire connections without cutting.

Another advantage is to be seen in the improved performance of themanufacturing method. In particular, the cycle time may be shortened byfar as the end-effector needs no longer to engage with the primarybuilding structure (e.g., to grip or clamp a strand of the primary meshstructure) for the purpose of connecting (welding) the secondary meshstructure to the primary mesh structure. By contrast, according to theinvention, the end-effector continuously rolls over the primary meshstructure for roll spot welding. In particular in contrast to therobotic system, described in WO 2017/153559 A1, according to thisinvention, it is no longer necessary to stop the end-effector at adedicated cross-wire position and to clamp the end-effector in thisposition in order to initiate the welding process. Further, it is notnecessary to cut the metal strand (secondary mesh structure), which hasbeen welded to the primary mesh structure after welding.

Moreover, performance may be improved by using more than oneend-effector in the robotic end-effector tool. In particular, tworobotic end-effectors may be used simultaneously or in parallel, forexample at opposite sides of the primary mesh structure. Preferably, thetwo end-effectors are then controlled such as their vertical and widthposition (with respect to the primary building structure) is identicalfor optimally balancing the applied forces. Each of the at least oneend-effector may be provided at an articulated robotic arm. The roboticarm is supported on a platform. The platform may be mobile. Inparticular, the platform may be configured for linear movement.Preferably, the platform may be moved by a drive motor, in particular oflinear actuator. Preferably, the platform may be moved in the direction,being parallel with a plane of the primary mesh structure. In case,e.g., two end-effectors are used, two different articulated arms serveas support structure, which are themselves supports on two differentplatforms.

The contact force or pressure of the robotic end-effector, with whichthe robotic end-effector is “pressed” or forced against the primary meshstructure (and which therefore is applied to the primary mesh structure)is measured. Preferably, the contact pressure is measured continuously.The contact pressure is measured and may be processed (in particularlocally) for providing contact force signals. The measured contact forcerepresents a contact force to be applied during rolling over the primarymesh structure of the robotic end-effector. The contact force signalsmay be used for control of the robotic end-effector. This serves thetechnical purpose, that a uniform contact force shall be applied allover the primary mesh structure. For example, in case it is detectedthat the primary mesh structure bounces or springs back another forceneeds to be applied for assuring proper welding.

Preferably, the contact force is measured continuously. The contactforce may be measured in such phases, where the end-effector rolls overthe primary mesh structure for roll spot welding, whereas in phases,where the end-effector is repositioned for welding the next strand(secondary mesh structure) and/or is configured to change to anothersecondary mesh structure item (for example to a secondary mesh structureitem with another diameter or to a secondary mesh structure item withanother material) the detection of the contact force may be interrupted.In still another embodiment, the contact force is measured continuouslyand permanently, but not all of the measured contact force signals aregoing to be processed by a processing entity, for example the processor.In particular, in phases where the end-effector does not touch theprimary mesh structure, it is not necessary to process the contact forcesignals.

The primary mesh structure (also abbreviated herein as primarystructure) may be and preferably is a set or series of two-dimensionalwire structures, that are not connected to each other yet. The primarymesh structure with the series of two-dimensional wire structures willbe connected to each other by means of applying the secondary meshstructure as suggested by the invention. The primary mesh structure mayalternatively be a 1D- or 3D mesh structure. The primary mesh structuremay comprise a variety of wires with different curvatures in differentextensions and/or with different radii. The primary mesh structure maybe generated by means of using a robot, based on a digital 3D model. The3D mesh structure may comprise concave and/or convex sections. Theprimary mesh structure may be of a reinforcement material. The primarymesh structure may preferably be steel. Alternatively, or in addition,bamboo, wood, carbon fiber, glass fiber or plastic material may be usedas primary mesh structure.

The secondary mesh structure (also abbreviated herein as secondarystructure) may be and preferably is a continuous wire or wire strand.The secondary mesh structure may be steel wire. The secondary meshstructure is preferably used to connect the series of primary meshstructure to generate the mesh structure. The term “mesh structure” isto be construed as that particular structure which needs to bemanufactured (from or with the primary and the secondary meshstructure). The secondary mesh structure may be connected to the primarystructure in various angles with respect to elements (wires) of theprimary structure. Preferably, a 90° connection is selected. However,angles in between 0 and 90° may be set and used. Alternatively, or inaddition, bamboo, wood, carbon fiber, glass fiber or plastic materialmay be used as secondary mesh structure. The secondary mesh structuremay comprise a set of different items. For example, a first secondarymesh structure item may be a steel wire in 6 mm, a second item may be awire in 8 mm, a third item may be wire in 12 mm etc. Typically, thesecondary mesh structure is an endless or continuous structure in theform of a strand. The secondary mesh structure preferably is provided oncoils. In a first embodiment, the coils for the different items of thesecondary mesh structure are directly mounted on a platform of therobotic end-effector and thus locally. In a second embodiment, the coilsfor the different items of the secondary mesh structure are stored orshelved separately from the platform with the respective end-effector.

The secondary structure is preferably applied continuously, i.e., thesecondary structure is connected as a continuous structure. Thesecondary mesh structure is not discrete and does not have a limitedlength. By contrast, the material, being provided to the end-effector iscontinuous. The secondary mesh structure may be cut to length afterbeing welded onto the primary mesh structure. The fact that thesecondary mesh structure is applied continuously in arbitrary directionsis crucial for load transfer. This is therefore, an important feature ofthe present invention.

In a preferred embodiment, the secondary mesh structure is not cut tolength while rolling over the primary mesh structure. In anotherpreferred embodiment, the secondary mesh structure is not cut to lengthbefore an outer side of the primary mesh structure has been reachedafter the process of rolling over the primary mesh structure hasstarted. This means, that typically, the process of rolling over startsat a first outer side (right/left side or bottom/upper side of theprimary mesh structure) and proceeds to the opposite side thereof (inthe examples above, correspondingly: left/right or upper/bottom side).The application of continuous secondary mesh material in continued withthe same strand of material of secondary mesh structure until therespective opposite side of the primary mesh structure has been reached.The secondary mesh structure may—but is not required to (as it couldalso be bent in the other direction) —only be cut to length after onerolling over process ends and the opposite side has been reached.

The rolling over process is typically repeated at a different position,e.g., when rolling over is performed in horizontal direction, then afirst rolling over process e.g., from left to right, may be performed inheight A, and a second rolling over process may be performed, e.g., inheight A+i, wherein i being an increment. The increment may be set byrequirements of the 3D model. Accordingly, if rolling over is performedin vertical direction, the rolling over may be repeated for a subsequentnext Y position, i.e., incremented position to the right or to the left.Also, in case the rolling over is to be performed in another angle, theend-effector will usually proceed until the opposite outer side of theprimary mesh structure has been reached, if it is not instructedotherwise by the processor.

In a preferred embodiment, the rolling over process is executed whilebending the secondary mesh structure in accordance with the outer formof the primary mesh structure in parallel. Preferably, the bending isexecuted by means of an anode of the welding unit. The anode may beconfigured as roller or rolling element, wherein the rotation axis ofthe anode is parallel to a surface of the primary mesh structure at thatpoint and/or orthogonal to the movement direction of the rolling overmovement (of the end effector).

It is possible to use more than one secondary mesh structure to beapplied and connected to the primary mesh structure in parallel. In apreferred embodiment, different items of secondary mesh structure may beprovided, for instance secondary mesh material items in differentdimensions and/or materials. For example, the first item may be providedfrom a first coil and a second item of the secondary mesh structure maybe provided from a second coil. The different items of secondary meshstructure are preferably processed by different end-effectors. So, forexample the first end-effector is configured for bending and welding thefirst item of secondary mesh structure and the second end-effector isconfigured for bending and welding the second item of secondary meshstructure.

The generated mesh structure is a two- or three-dimensional meshstructure. The generated mesh structure may be or may comprise a metalstructure. The generated mesh structure may be used for reinforcement ofconcrete structures in construction engineering or in otherreinforcement systems. The generated mesh structure may be but is notrequired to be filled with concrete later. The generated mesh structuremay be used for example in exhibition stand construction, in facadeengineering and/or in furniture construction or related fields.

The cross welding(s) preferably are cross-wire weldings. But forspecific applications, the primary structure may also be anotherstructure, not a wire structure, like e.g., a surface structure like aplate or may be made from other material, than metal wire, like e.g.,bamboo, as mentioned above.

The term “roll spot welding” relates to welding the secondary structureto the primary structure. Roll spot welding is done without interferingwith the primary structure. It is not necessary to grip or clamp theprimary structure of parts thereof for the welding process. The onlyprerequisite for the welding process is that the cathode of the weldingunit of the end-effector needs to be in contact with the primarystructure and in particular with an element of the primary structureduring the welding process.

As described above, roll spot welding may imply that the secondary meshstructure is to be bent when being welded to the primary mesh structurein order to align the secondary mesh structure to the primary meshstructure. With other words, if the primary mesh structure for exampleshows a first concave section, followed by a second convex section, thesecondary mesh structure needs to be adapted to and aligned with thiscurvature. Accordingly, also the secondary mesh structure will be bentso to provide a first concave section and a second convex section. Withthe bending process, it is assured that the secondary mesh structure“follows” the primary mesh structure.

The process of “rolling over” the primary mesh structure relates to themovement of the end-effector over said structure. The trajectory mightbe defined by a 3D model. The rolling over might be executed in avariety of different directions. Preferably, two main directions may bedefined. In a first scenario, in which the primary mesh structure has(mainly) vertically extending elements, the secondary mesh structure isto be applied horizontally and might be ‘rolled over’ from left to rightor vice versa. In this first scenario, the process of rolling overstarts on the one side of the structure (e.g., to the right) andcontinues to the left until it ends at the opposite side (at the leftmost side). The process may then be re-iterated in the next height withthe next secondary mesh structure item. In a second scenario, in whichthe primary mesh structure has (mainly) horizontally extending elements,the secondary mesh structure is to be applied vertically and might be‘rolled over’ from top to bottom or vice versa. In this second scenario,the process of rolling over starts on the one side of the structure(e.g., bottom) and proceeds to the upward end until it ends at theopposite side (at the top most side). Also, here, the process may thenbe re-iterated in Y direction with the next secondary mesh structureitem. However, these two scenarios are not the only ones, beingfeasible. It is also possible that the primary and/or secondary meshstructure may be provided or applied in other angles.

The sequence of interrupted welding processes may be and preferably isexecuted in one direction from one end or side of the primary meshstructure to the opposite side. In this phase (rolling over) thesecondary mesh structure is usually not cut to length and is processedin a continuous form. After having completed one row or column(according to the respective mesh structure) of secondary mesh structurewelding, there exist two options:

-   -   1. The wire, i.e., the secondary mesh structure is bent with a        180° so that the same wire may be used for the next line or row        in the mesh structure.    -   2. Otherwise, the wire, i.e., the secondary mesh structure is        not bent, but is cut to length.

Subsequently, the next row or line may be started with a new item ofsecondary mesh structure.

The control signals serve for—in particular closed loop—control of theend-effector.

According to a preferred embodiment of the present invention, thecontrol signals comprise first control signals and second controlsignals. The control signals may also comprise at least two sections:

-   -   1. first control signals for controlling the movement of the        end-effector as represented by a trajectory (when rolling over        the primary mesh structure) and    -   2. second control signals, indicating welding parameters for        executing the welding process and for controlling the welding        process and in particular a time interval for the welding        process. In particular, the starting time point, the end time        point and/or duration of the welding process in the roll spot        welding may be configured and/or controlled. Alternatively, or        in addition, further parameters for the welding process,        comprising voltage, current, duration etc. may be controlled.

In another preferred embodiment, the first control signals aredetermined in response to the measured contact force. The first controlsignals are determined such that the target contact force equals themeasured contact force. In particular, the first control signals are orcomprise instructions for instructing a set of actuators for positioningthe end-effectors with the welding unit to adapt and/or control thecontact force in order to reach the target contact force. Thus, firstcontrol signals are used to control a selection of the second controlsignals, in particular: the contact force. The instructed contact forceis dependent on the stiffness or rigidity of the primary mesh structure.Generally, the less rigid and more compliant a primary mesh structureis, the more the robot (end effector) has to deviate from the (preset)trajectory to achieve the target welding force.

The control signals may be classified in static control signals, beingconstant during the course of rolling over, and dynamic control signals.The static control signals may be determined from a 3D model. Thedynamic control signals are variable and may change during the course ofrolling over. In particular, the dynamic control signals arecontinuously adapted in reply to the measured contact force. The dynamiccontrol signals comprise the instructed contact force.

In a preferred embodiment the contact force is closed loop controlleddynamically. Thus, the contact force, being applied in a first weldingprocess within the sequence of welding processes may differ from thecontact force, being applied in a second welding process, dependent onthe position in space, the engagement of other robotic end-effectors,being used in parallel and/or other criteria.

In a preferred embodiment, the first control signals for controlling thewelding for generating the mesh structure are issued by a processingunit or a processor and are generated on the basis of athree-dimensional model and/or on the basis of the measured contactforce. The trajectory for the end-effector for applying the second meshstructure to the primary mesh structure is calculated on the basis ofthe measured contact force in comparison the target contact force, whichis required to be applied according to a three-dimensional model.

The second control signals may be provided from the same of from adifferent processor. The second control signals may be determined bymeans of the three-dimensional model and/or may be static.Alternatively, or in addition, the second control signals are calculatedby taking into account measured (and may be dynamic) parameters of theend-effector. The measured parameters may comprise the contact force.The contact force represents the force which is applied for pressing theend-effector onto the primary mesh structure in the direction beingperpendicular to the respective surface plane of the primary meshstructure.

Generally, in a preferred embodiment, the welding is closed loopcontrolled in an adaptive way. The control signals are part of a controlloop for controlling/regulating disturbance variables/influences such asin particular the varying contact pressure/force. Alternatively, or inaddition, also other disturbance variables like wire thickness changes(due to manufacturing tolerances) may be controlled. As a result, theseprocesses deliver a reliably high weld quality,

For example, signals of optical sensor(s) at the head of theend-effector may be processed by the processor to analyze the electrodedegradation of the welding unit. Also, wear of the electrodes may beanalyzed—preferably for initiating counter measures.

The control signals and in particular the first control signals may begenerated in response to the measured contact force and/or positionsignals. Further, the control signals may be generated in response tooptical signals, detected form optical sensors, to thermal signals,detected by thermal sensors, and/or to inductive signals, detected byinductive sensors. The control signals may be determined by theprocessor in response to received signals, at least in response toposition and/or contact force signals. The control of the contact forceis relevant for in this invention, since first no clamps are used forfixing an end-effector or a part thereof to the workpiece to beprocessed (here: primary mesh structure). Second the work piece is notfixed statically, meaning that the primary mesh structure is resilientor compliant and may move if a force is applied in direction of thenormal of the primary mesh structure onto the same.

Preferably, there is an active measuring of the contact force and therespective and corresponding real-time adaptive positioning of theend-effector with the welding unit (by means of controlling actuators(drive motors) for placement of the end-effector). Preferably, thecontact force is measured for every or for selected points on thetrajectory, the end-effector is required to travel (and/or the contactforce is measured continuously or at selected time points). The“selected” time points may be preset and may be determined to equal thewire crossing locations (crossing of primary mesh structure andsecondary mesh structure).

The integration of additional sensors in the end-effector may be used toimprove the robustness and complement the system:

-   -   An optical sensor and/or inductive sensor can be used to        measure, when a welding command can be executed. This may then        serve as an alternative to receiving the initiation signal for        the welding command from the 3D mode.    -   A thermal sensor can be used to improve the durability of the        resistance welding parts that are exposed to wear and tear        (e.g., anode and cathode). The sensor can measure the        temperature of the parts and regulate cooling.

The processor serves inter alia for dynamically generating the controlsignals, in particular the first control signals, for robotic control.The processor may be implemented on the robotic end-effector tooldirectly or may be implemented on a separate computing instance, beingin data exchange with the robotic end-effector tool. In particular, theprocessor may be distributed over a plurality of computing entities andmay for example be implemented directly on the end-effectors of theend-effector tool, directly. In another embodiment, a (e.g., central)server may be provided, being in data exchange with the end-effectortool and/or its components.

The processor may be a central processing unit and may comprise hardwareand software components, the latter also in the form as embeddedsoftware and/or algorithms. The CPU may comprise or may be provided as amicroprocessor, a field programmable gate array (an acronym is “FPGA”)or an application specific integrated circuit (an acronym is “ASIC”).The CPU may serve to execute different internal functions of computingentities in the context of robotic mesh generation. The processor, interalia, may serve to generate the control signals, in particular thedynamic control signals, which may vary over time during rolling overand/or to instruct components of the end-effector.

Alternatively, or in addition to this, the processor may further bedesigned to generate a set of alarm messages in case the sensor signalshave been evaluated and indicate problematic state of the end-effectorand to prepare the alarm messages to be displayed on a display unit,i.e., to calculate a graphical representation of the instant state ofthe end-effector and/or generated mesh for being displayed on e.g., amonitor of a remote central server.

Alternatively, or in conjunction with the above, the method may furthercomprise the step of:

-   -   generating a virtual representation of the generated mesh        structure, based on optical sensors.

The virtual representation of the generated mesh, being generated sofar, may be stored and serves to provide an automatically generateddocumentation of the mesh generation procedure carried out by theend-effector(s). Alternatively, or in conjunction with the above, thesignals of the optical sensors and/or the virtual representation may beused to automatically validate and, if needed, correct the procedure.Moreover, by using the optical sensor signals and/or the virtualrepresentation, the processor may automatically compare the actual stateof the mesh with the target state as per 3D model and in case ofdeviations, may initiate counter measures and/or to inform the operator.With this, it is possible to track, store and/or verify the meshgeneration procedure with intermediate steps and thus also during theprocess of mesh generation.

The robotic end-effector tool may comprise one or more end-effector(s).In the latter case, e.g., two end-effectors may be used for applying twodifferent items of the secondary mesh structure from opposite sides tothe primary mesh structure so that tilting moments (due to the appliedforce, mainly extending in a horizontal extension) for the primary meshstructure may be eliminated as much as possible. Therefore, the twoend-effectors may be positioned “in common” with respect to the primarymesh structure. In particular, their movement and trajectory may becontrolled such as their Y and Z position in space may be nearly thesame, when assuming that the primary mesh structure mainly extends in aplane in Y- and Z-dimension (although the primary mesh structure maycomprise curvatures and the secondary mesh structures are configured to“follow” this curvature).

In a preferred embodiment, the end-effector may be mobile itself, but isnot required to be mobile itself, since it may be attached to a mobileplatform. A robot serving as end-effector or end-effector tool may e.g.,be fixed or mounted on a ground or on a linear track and/or may becombined with a mobile unit for providing mobility.

According to a preferred embodiment, the welding unit is a resistancewelding unit. Resistance welding is favored since it is an economicalway to join two pieces of metal wire. Resistance welding allows for ahigh speed, repeatability/reproducibility and robotic integration.Alternatively, the welding unit may be configured as a gas metal arcwelding unit or a tying gun for providing a tying connection. Thewelding unit is preferably configured for roll spot welding. Further,preferably, the welding unit is configured for joining two metal wiresor strands or other mesh components. The weld is made by conducting astrong current through the metal combination to heat up and finally meltthe metals at localized point(s). The welding process is defined by aset of parameters, comprising welding current, welding time, welding orcontact force, and/or material properties, like diameter, type ofmaterial, surface coatings and/or others.

The contact force influences the resistance welding process by itseffect on the contact resistance at the interfaces and on the contactarea (or point) due to deformation of the primary and secondary meshmaterials. The elements of the primary and secondary mesh structuresmust be compressed with a certain force at the weld spot to enable thepassage of the current. If the welding force is too low, expulsion mayoccur immediately after starting the welding current due to fact thatthe contact resistance is too high, resulting in rapid heat generation.If the welding force is high, the contact area will be large resultingin low current density and low contact resistance that will reduce heatgeneration and the size of weld nugget. In consequence, it is to beassured that the correct contact force is to be applied for providinghigh quality welding results and thus high-quality reinforcementstructures.

According to another preferred embodiment, the secondary mesh structureis bent by means of the end-effector during rolling over the primarymesh structure, in particular according to a curvature of the first meshstructure.

According to still another preferred embodiment, rolling over theprimary mesh structure is not interrupted by a cutting process. Further,the step of ‘rolling over’ does not comprise cutting the secondary meshstructure to length before the end of the primary mesh structure isreached. For example, if the secondary mesh structure is to be welded ina horizontal direction to the primary mesh structure, the primary meshstructure will not be cut before the right or left and of the primarymesh structure is reached. Depending on the digital data of thethree-dimensional model, it is not necessary to cut the secondary meshstructure after having completed “one row” within a sequence ofinterrupted welding processes. It is possible to bend the secondary meshstructure in the opposite direction to continue with rolling over (theprimary mesh structure) with the same secondary mesh structure to beapplied in the opposite direction (Y direction), and thus starting thenext row.

Preferably, the sequence of interrupted welding processes is appliedwith one and the same endless secondary mesh structure. This means, thatthe secondary mesh structure is welded in a continuous format whichsignificantly improves statical requirements (transfer of forces). Thus,during the sequence of interrupted welding processes, the secondary meshstructure remains in endless form and is not cut.

In another preferred embodiment, a welding process is instructedautomatically in response to a digital control signal, wherein thedigital control signal is generated by processing a 3D mesh model. Inanother embodiment, the welding process or selected welding processesare only initiated in response to an initiation signal. The initiationsignal may be provided, for example, on a user interface by a humanoperator.

In a first preferred embodiment, only one end-effector is used and theend-effector tool comprises only one end-effector.

In second preferred embodiment, and as mentioned above, the roboticend-effector tool comprises at least two separate end-effectors at twodifferent robotic arms, wherein the at least two separate end-effectorsare used in parallel for applying different items of the secondary meshstructure to the primary mesh structure, in particular on the sameheight and/or in the same longitudinal extension from opposite sides.

In a first embodiment, the two or more end-effectors are working withdifferent secondary mesh structure item (for example, secondary meshstructures with different diameter and/or different material). In asecond embodiment, the two or more end-effectors are working on oppositesides of the primary mesh structures on the same height level and/or atnearly the same width position (Y axis). Technical advantage is abalance of applied forces to the primary mesh structure.

According to another preferred embodiment, the contact force is measuredby means of a force measurement sensor, which is attached at a head ofthe robotic end-effector, in particular in an area where the contactforce is applied.

Generally, the force measurement sensor (also mentioned shortly hereinas ‘force sensor’) may be implemented as load cell. The forcemeasurement sensor can be mounted in various positions at the head ofthe end-effector. It is important to calibrate it appropriately so that,for example, the dead weight of the end-effector can be compensated.Preferably, the force sensor is mounted between the robot's arm (wristof the robot) and the end-effector. In this position, all forces on therobot are diverted or guided to the robot. The orientation of the forcemeasurement sensor then also corresponds or is aligned to the coordinatesystem of the robot thereby easing the calibration process. Moreover,the force measurement sensor is also protected from the high currents ofcontact welding. In particular, the contact force is measured betweenthe secondary wire pressing onto the primary structure and the rollingelectrode (anode). The force direction is from the center of the rollingelectrode, normal to curve that represents the desired trajectory of thesecondary wire being applied.

According to a preferred embodiment, the secondary mesh structure iswelded to the primary mesh structure horizontally or vertically or in anangle between 0° and 90° with respect to a direction of an element ofthe primary mesh structure. This makes it possible that the meshstructure is generated according to variable conditions so that a highdegree of flexibility may be reached.

In still another preferred embodiment, the at least one end-effector isadapted:

-   -   to weld the secondary mesh structure onto the primary mesh        structure;    -   to weld-off elements (wire) of the primary mesh structure;    -   to move and in particular to roll over the primary mesh        structure, by translatory and/or rotational movements, depending        on the curvature of the primary mesh structure;    -   to bend the secondary mesh structure, according to the curvature        of the primary mesh structure, in particular in case the primary        mesh structure is not planar, and/or at the end of the        structure; and/or    -   to cut the secondary mesh structure after completion of the        sequence of interrupted welding processes.

According to another preferred embodiment, the at least one end-effectorcomprises an anode and a cathode, wherein the anode is provided asrotating roller and the cathode is provided as rotating dog or carrier,which hops or skips to a next element of the primary mesh structure.

According to a preferred embodiment, the anode serves as part of thewelding unit (the welding unit comprises anode and cathode) and inaddition as bending unit. This has the advantage that the end-effectormay be constructed with less parts and may be cheaper to manufacture.The bending unit is a metallic component, preferably copper, which ismounted rotatably so to rotate around a rotational axis which extendsparallel to the surface plane of the primary mesh structure and/orperpendicular to the movement direction of the end-effector (rollingover direction).

The carrier may be spring-mounted. The carrier may be provided in arectangular or in another lengthy form. The respective next element ise.g., a vertical element of the primary mesh structure over which theend-effector rolls in a horizontal direction. The carrier then hops fromone vertical element of the primary mesh structure to the next. Inanother embodiment, the secondary mesh structure is to be applied in avertical direction and main elements of the primary mesh structure arein the horizontal direction. Thus, the secondary mesh structure may beapplied in an upwards or downwards direction to the primary meshstructure. Here, the carrier hops from one horizontal element of theprimary mesh structure (or row) to the next. Also, an oblique rollingover direction may be instructed. In this case, it would potentiallyneed some light adaptation, such as e.g., the carrier could also beconfigured a roll like the anode or it could have some spring-rotatingmechanism that enables it to adjust to different angles.

The end-effector may preferably comprise a rebar threader, which inconfigured for providing the secondary mesh structure (in the form ofrebar wire) to the end-effector for the purpose of bending and welding.The rebar threader is a metallic component for providing the secondarymesh structure through a hollow structure, in particular an aperture.The rebar threader supports the wire, holding it at the correct height,mainly parallel to the primary mesh structure. Additionally, it acts asa bending point (bending pin) while bending the secondary wire.Additionally, it enables to make sure that there is no collision betweenthe wire feed of the secondary wire (secondary mesh structure) to theprimary mesh structure, since the robot can rotate the rebar threaderaway from the structure.

In a preferred embodiment, the at least one robotic end-effector isplaced on a mobile platform. The platform is not legged or wheeled. Themobile platform is preferably configured for lateral movement,preferably in one axis (Y axis). Thus, the platform is transferable by alinear actuator for linear movement, in particular parallel to a planeof the primary mesh structure. In more complex scenarios, the mobileplatform may be movable also in other directions, for example in X-, Y-and/or even Z-axis. In another preferred embodiment, the at least onerobotic end-effector may remain static and is not placed on a mobileplatform and the primary mesh structure is moved with respect to therobot. Thus, the rolling-over movement may be accomplished by relativemovement between the primary mesh structure and the end-effector.

According to a preferred embodiment, the robotic end-effector is movedalong a desired trajectory over the primary mesh structure according tocontrol instructions which are calculated on the basis of a digital3D-model and adapted based on the contact force measured. Preferably,the trajectory is preset and defined by the three-dimensional model.However, the controller instructions for controlling the weldingprocesses, and in particular the position of the end-effector with thewelding unit for initiating or executing the welding, are not preset andare calculated dynamically in response to measured signals at the headof the end-effector in order to achieve a desired contact force. Theother welding settings (like: current, welding time, welding startsignal) are preferably preset from the 3D model.

In another aspect the present invention refers to a robotic end-effectortool for generating a mesh structure for use in constructionalengineering, like architecture, engineering and/or construction, inparticular for use in reinforcement systems, which is configured to beused in a method according to any of the preceding method claims,comprising:

-   -   at least one end-effector, being movable in six degrees of        freedom for applying an endless secondary mesh structure to the        provided primary mesh structure continuously by roll spot        welding,        -   wherein the at least one end-effector further comprises:        -   a welding unit, configured for welding the secondary mesh            structure to the primary mesh structure at pre-defined            connection positions to generate cross-wire connections by            means of a welding unit, in particular a resistance welding            unit; preferably, the welding unit comprises an anode and a            cathode.        -   contact force sensors, configured for measuring the contact            force of the robotic end-effector, being applied to the            primary mesh structure during rolling over the primary mesh            structure;    -   a processor for closed loop control of the at least one robotic        end-effector by means of control signals, wherein the control        signals are generated at least in part in response to the        measured contact force.

In a preferred embodiment, the welding unit and in particular the anodethereof serves a bending unit or is configured for bending the secondarymesh structure while rolling over the primary mesh structure. The anodemay be configured as roller with a rotation axis being parallel to theplane of the primary mesh structure. The rotation axis may be orthogonalto the movement direction of the end-effector.

In another aspect, the invention relates to a computer programcomprising a computer program code, the computer program code whenexecuted by a processor causing a robotic end-effector tool according tothe directly preceding claim to perform the steps of the method of anyof the preceding method claims, when the robotic end-effector isprovided with a primary mesh structure and in case an initiation signalis provided. The instructing steps and the controlling are preferablycomputer-implemented. Thus, the method is computer-implemented,provided, that the primary mesh structure is provided to theend-effector.

The properties, features and advantages of this invention describedabove, as well as the manner they are achieved, become clearer and moreunderstandable in the light of the following description andembodiments, which will be described in more detail in the context ofthe drawings.

In another first aspect or embodiment (application number EP 20 171861.6), the invention relates to a primary building structurefabrication system, comprising:

-   -   a processing unit; and    -   at least one manipulator, in particular the robotic        end-effector;

wherein, the processing unit is configured to receive fabricationinformation; wherein, one or more manipulators are configured tofabricate a plurality of sections of a primary building structure (alsocalled a primary mesh structure); wherein, each section comprises atleast one strand (in particular wire strand); wherein, the at least onestrand comprises one or more of wire, rod or band; and wherein, thefabrication of the plurality of sections comprises utilization of thefabrication information.

In this first embodiment, the manipulator of the at least onemanipulator may be configured to align one or more sections of theplurality of sections on a platform, and wherein the alignment comprisesutilization of the fabrication information.

In this first embodiment, the manipulator may be configured to positiona first section of the plurality of sections on the platform, andwherein the manipulator is configured to align the one or more sectionsrelative to the first section.

In this first embodiment, the manipulator of the at least onemanipulator may be configured to fix the plurality of sections to theplatform.

In this first embodiment, the manipulator may be configured to fix theplurality of sections to the platform such that they can subsequently bereleased from the platform.

In this first embodiment, fixation of the plurality of sections to theplatform by the manipulator may comprise one or more of: gluing;clamping; tying; utilizing magnets; MIG/MAG welding; or contact welding.

In this first embodiment, the at least one strand of a section comprisesa first strand and comprises a second strand, and wherein to fabricatethe section the one or more manipulators may be configured to fix one ormore interconnecting strands the first strand and to the second strand.

In this first embodiment, to fabricate a section the one or moremanipulators may be configured to bend the at least one strand of thesection.

In this first embodiment, the at least one strand of a section maycomprise a first strand and comprises a second strand, and wherein tofabricate the section the one or more manipulators may be configured tobend the first strand and/or the one or more manipulators are configuredto bend the second strand.

In this first embodiment, the at least one strand of a section comprisesa first strand and comprises a second strand, wherein to fabricate thesection the one or more manipulators are configured to fix a firstinterconnecting strand to the first strand and fix the firstinterconnecting strand to the second strand; wherein the one or moremanipulators are configured to bend the first strand and/or bend thesecond strand; and wherein the one or more manipulators may beconfigured to fix a second interconnecting strand to the first strandand fix the second interconnecting strand to the second strand, suchthat a section of the first strand between the first interconnectingstrand and the second interconnecting strand and/or a section of thesecond strand between the first interconnecting strand and the secondinterconnecting strand is bent, wherein the bending and fixing comprisesutilization of the fabrication information.

In this first embodiment, the system comprises a stabilization platform,and wherein to fabricate a section the one or more manipulators areconfigured to bend the at least one strand of the section whilst atleast a part of the at least one strand is in contact with thestabilization platform such that the section conforms to a surface planeof the stabilization platform.

In this first embodiment, the at least one strand of a section comprisesa first strand and comprises a second strand, wherein after the one ormore manipulators have bent the first strand and/or bent the secondstrand, the one or more manipulators may be configured to align thefirst strand relative to the second strand, wherein the alignmentcomprises a movement and/or a further bending of the first strand and/orthe alignment comprises a movement and/or a further bending of thesecond strand, and wherein the alignment may comprise utilization of thefabrication information.

In this first embodiment, the alignment may comprise an alignment of aplurality of segments of the first strand relative to a plurality ofsegments of the second strand, and wherein after a segment of the firststrand is aligned relative to a segment of the second strand, thesegment of the first strand is fixed to the segment of the second strandwith an interconnecting strand.

In this first embodiment, the one or more manipulators are configured tofix the interconnecting strand to the segment of the first strand and tothe segment of the second strand.

In this first embodiment, the at least one strand of a section maycomprise a first strand and comprises a second strand, and wherein theone or more manipulators are configured to bend the first strand and/orbend the second strand whilst an end of the first strand is fixedrelative to an end of the second strand.

In this first embodiment, the manipulator may be configured to fix apart of one strand to a part of another strand and/or fix one part ofstrand to another part of the same strand, wherein the fixationcomprises: tying; MIG/MAG welding; or contact welding.

In this first embodiment, the one or more sections are fabricated andaligned on the platform such that at least one part of the at least onestrand for each section of the one or more sections is located at ornear a corresponding at least one of a plurality of intersection pointsdefined within the fabrication information.

In this first embodiment, the at least one of the plurality ofintersection points defined within the fabrication information isuseable for the alignment and/or attachment of a feed strand to theprimary building structure formed from the plurality of sections.

In second embodiment a wire section fabrication manipulator may beprovided, wherein the manipulator is configured to be controlled tofabricate a section of a primary building structure out of at least onestrand; wherein the at least one strand comprises one or more of wire,rod or band; and wherein the control comprises utilization offabrication information.

In this second embodiment, the manipulator may be configured to bend theat least one strand of the section.

In this second embodiment, the manipulator may comprise a first strandinteractor and a second strand interactor, wherein the first strandinteractor is configured to support, hold or grasp a first strand of theat least one strand of the section and wherein the second strandinteractor is configured to support, hold or grasp a second strand ofthe at least one strand of the section, and wherein the first strandinteractor is configured to move relative to the second strandinteractor on the basis of the fabrication information.

In this second embodiment, the first strand interactor may comprise afirst part and a second part and the second strand interactor comprisesa first part and a second part, wherein the first part of the firststand interactor is configured to contact a first side of the firststrand and the second part of the first stand interactor is configuredto contact a second side of the first strand opposite to the first side,and wherein the first part of the second stand interactor is configuredto contact a first side of the second strand and the second part of thesecond stand interactor is configured to contact a second side of thesecond strand opposite to the first side.

In a third embodiment, a wire section alignment manipulator may beprovided, wherein the manipulator is configured to be controlled toalign one or more sections of a plurality of sections of a primarybuilding structure on a platform; wherein each section comprises atleast one strand; wherein the at least one strand comprises one or moreof wire, rod or band; and wherein the control comprises utilization offabrication information.

In this third embodiment, the manipulator may be configured to becontrolled to position a first section of the plurality of sections onthe platform, and wherein the manipulator is configured to align the oneor more sections relative to the first section.

In this third embodiment, the manipulator may be configured to becontrolled to fix the plurality of sections to the platform.

In a fourth embodiment, a method of fabricating a primary buildingstructure is provided, the method comprising:

a) receiving by a processing unit fabrication information; and

b) fabricating with a manipulator of at least one manipulator aplurality of sections of a primary building structure; wherein, eachsection comprises at least one strand; wherein, the at least one strandcomprises one or more of wire, rod or band; and wherein, the fabricatingthe plurality of sections comprises utilizing the fabricationinformation.

Another fifth aspect or embodiment (according to application number EP20 171 865.7) of the invention relates to a building structurefabrication system for feed wire, feed rod or feed band, the systemcomprising:

-   -   a processing unit; and    -   a manipulator; wherein, the processing unit is configured to        receive assembly information; wherein, the manipulator is        configured to align a feed to a primary structure at a plurality        of intersection points; wherein, the feed is a feed wire, feed        rod, or feed band; wherein, the primary structure is a primary        wire structure, primary rod structure, or primary band        structure; and wherein, the alignment of the feed to the primary        structure at the plurality of intersection points comprises        utilization of the assembly information.

In this fifth embodiment, the manipulator may be configured to align thefeed to the primary structure at a first intersection point of a pair ofadjacent intersection points and then align the feed to the primarystructure at a second intersection point of the pair of adjacentintersection points.

In this fifth embodiment, the manipulator may be configured to bend thefeed, and wherein alignment of the feed to the primary structure at theplurality of intersection points comprises a bending of the feed betweenat least one pair of adjacent intersection points.

In this fifth embodiment, the manipulator may be configured to attachthe feed to the primary structure at the plurality of intersectionpoints.

In this fifth embodiment, attachment of the feed to the primarystructure at the plurality of intersection points comprises utilizationof the assembly information.

In this fifth embodiment, the manipulator is configured to attach thefeed to the primary structure at a first intersection point of a pair ofadjacent intersection points and then attach the feed to the primarystructure at a second intersection point of the pair of adjacentintersection points.

In this fifth embodiment, attachment of the feed to the primarystructure at the plurality of intersection points may comprise a bendingof the feed between at least one pair of adjacent intersection points.

In this fifth embodiment, the manipulator may be configured to attachthe feed to the primary structure at a first intersection point of apair of adjacent intersection points and then bend the feed between thepair of adjacent intersection points and then attach the feed to theprimary structure at a second intersection point of the pair of adjacentintersection points.

In this fifth embodiment, the manipulator may be configured to move atleast one wire or rod or band segment of the primary structure, andwherein attachment of the feed to the primary structure at the pluralityof intersection points comprises a movement of the at least one wire orrod or band segment of the primary structure.

In this fifth embodiment, the manipulator may be configured to move theat least one wire or rod or band segment of the primary structure suchthat a part of the at least one wire or rod or band segment ispositioned at a corresponding at least one intersection point, such thatthe feed is attached to the at least one wire or rod or band segment atthe at least one intersection point.

In this fifth embodiment and also in other embodiments mentioned herein,attachment of the feed to the primary wire structure at the plurality ofintersection points comprises: tying; MIG/MAG welding; or contactwelding.

In this fifth embodiment, the system comprises at least one sensordevice which may be configured to determine manipulator information,wherein the manipulator information comprises one or more of: a locationof the manipulator relative to at least one intersection point; adistance between the manipulator and at least one part of the primarystructure; a distance between the manipulator and at least oneintersection point; a determined contact between the manipulator and atleast one part of the primary structure; a contact force between themanipulator and at least one part of the primary structure; a torquebeing applied to the manipulator, and wherein the alignment of the feedto the primary structure at the plurality of intersection pointscomprises utilization of the manipulator information.

In this fifth embodiment and also in other embodiments, mentionedherein, the system comprises at least one sensor device configured todetermine manipulator information, wherein the manipulator informationcomprises one or more of: a location of the manipulator relative to atleast one intersection point; a distance between the manipulator and atleast one part of the primary structure; a distance between themanipulator and at least one intersection point; a determined contactbetween the manipulator and at least one part of the primary structure;a contact force between the manipulator and at least one part of theprimary structure; a torque being applied to the manipulator; andwherein the attachment of the feed wire to the primary structure at theplurality of intersection points comprises utilization of themanipulator information.

In a sixth embodiment, a manipulator is provided for feed wire, feed rodor feed band, wherein the manipulator is configured to be controlled toalign a feed wire, feed rod or feed band to a primary structure at aplurality of intersection points; wherein the primary structure is aprimary wire structure, primary rod structure, or primary bandstructure; and wherein the alignment of the feed wire, feed rod or feedwire to the primary structure at the plurality of intersection pointscomprises utilization of assembly information.

In the sixth embodiment, the manipulator comprises a roller configuredto engage with and roll along the feed wire or feed rod or feed band.

In the sixth embodiment, the manipulator comprises a conduit section (inparticular a rebar threader) through which the feed wire or feed rod orfeed band is configured to run.

In the sixth embodiment, the roller and conduit section are part of ahead portion of the feed manipulator (also called end-effector).

In the sixth embodiment, the manipulator comprises a transformer.

In the sixth embodiment, the manipulator comprises a cathode systemand/or an anode system.

In the sixth embodiment, the roller is part of the part of the anodesystem.

In the sixth embodiment, the manipulator comprises a cathode copperplate that is part of the cathode system and is arranged adjacent to theroller.

In the sixth embodiment, the manipulator comprises a clamp configured toclamp a wire or rod or band segment of the primary building structure tothe feed wire or feed rod or feed band at or in the vicinity of anassociated intersection point.

In the sixth embodiment, the clamp is part of the cathode system.

In a seventh embodiment, a method of fabricating a building structure isprovided, the method comprising:

-   -   receiving by a processing unit assembly information; and    -   aligning with a manipulator a feed to a primary structure at a        plurality of intersection points, comprising utilizing the        assembly information; wherein, the feed is a feed wire, feed        rod, or feed band; and wherein, the primary structure is a        primary wire structure, primary rod structure, or primary band        structure.

In an eight aspect or embodiment (according to application number EP 20205 631.3), the invention relates to a method for generating a meshstructure, comprising the steps of:

-   -   providing a first mesh structure, the first mesh structure being        a two- or three-dimensional mesh structure;    -   processing a mesh geometry of the first mesh structure based on        an input parameter set to define an operational environment; and    -   generating a set of robot instructions to apply additional        material to the first mesh structure based on the defined        operational environment, the additional material being used for        modifying the first mesh structure in order to provide a second        mesh structure.

So, densification according to the suggestion presented herein, can alsomake sense in terms of the geometry of the structure regarding thefilling. An overhanging structure might need a denser mesh on one side,to prevent loss of concrete during filling, whereas on the other side,it can have the minimal, structural relevant, reinforcement. Generally,the additional material may be used to modify the first mesh structurein order to provide a second mesh structure. Modifying, according to afirst embodiment may comprise adding material and thus a densificationof the first mesh structure. In a second embodiment, the step ofmodifying may comprise removing material form the first mesh structureto provide a lighter second mesh structure with less material. In thiscase, modifying may be performed by taking away material form the firstmesh structure or by not adding additional material. The second meshstructure may be the first mesh structure with modifications, forexample, with more material than the first mesh structure fordensification reasons. For example, more feed wire may be added to thefirst mesh structure or more wire may be added to the strands. The feedwire and/or the wire for the strands may be of variable diameter,variable length, different material than the material of the first meshstructure, or the like. The additional material may be applied to thefirst mesh structure in a horizontal and/or vertical direction. Byattaching additional material, it is, for example, possible to densifythe first mesh structure according to specific requirements. Forexample, if a part of the first mesh structure needs to be densified,additional material is applied to this part of the first mesh structurewhile keeping the other parts of the first mesh structure unchanged.Thus, a second mesh structure is obtained which comprises a moredensified part compared to the remaining parts.

In this eighth embodiment, the method may further comprise:

-   -   applying the additional material at a defined location of the        first mesh structure based on the set of robot instructions        using a robotic system in order to provide the second mesh        structure.

In this eighth embodiment, applying the additional material may beperformed iteratively in order to provide the second mesh structure.

In this eighth embodiment, providing the first mesh structure maycomprise providing a pre-constructed mesh structure as the first meshstructure.

In this eighth embodiment, providing the first mesh structure maycomprise constructing an initial mesh structure and providing theconstructed initial mesh structure as the first mesh structure.

In this eighth embodiment, the input parameter set is directed to acharacteristic of the second mesh structure to be provided.

In this eighth embodiment, the input parameter set indicates astructural analysis with regard to the second mesh structure, a forceflow of the second mesh structure, an orientation of the second meshstructure, and/or a set of thresholds regarding an amount of materialbeing used for the second mesh structure.

In this eighth embodiment, the operational environment defines an amountof the additional material to be added to the first mesh structure, atype of material to be used as the additional material, spatialinformation indicating a spatial position where to add the additionalmaterial to the first mesh structure to provide the second meshstructure, and/or type of connection.

In this eighth embodiment, the amount of the additional material to beadded to the mesh structure, the type of material to be used as theadditional material, and/or the type of connection are positiondependent and in particular depend on a position where the additionalmaterial is to be added to the first mesh structure.

In this eighth embodiment, applying the additional material at thedefined location of the first mesh structure comprises gravity-basedapplication of the additional material, spraying the additionalmaterial, applying the additional material on top of the first meshstructure, and/or attaching a tailored patch to the first meshstructure, the tailored patch representing the additional material.

In this eighth embodiment, the gravity-based application of theadditional material comprises guiding a flexible material over the firstmesh structure to provide the second mesh structure.

In this eighth embodiment, the method may further comprise:

-   -   transmitting the generated set of robot instructions to at least        one robot, the at least one robot using the transmitted set of        robot instructions to provide the second mesh structure.

In this eighth embodiment, if the generated set of robot instructions istransmitted to at least two robots (also called robotic end-effectors),the at least two robots work in parallel to provide the second meshstructure.

In this eighth embodiment, the generated set of robot instructionscomprises a time constant, the time constant indicating a time when theat least one robot starts processing the transmitted set of robotinstructions to provide the second mesh structure.

In a ninth embodiment, a processing unit is provided for generating amesh structure, the processing unit configured to use a provided firstmesh structure and to perform the steps of:

-   -   processing a mesh geometry of the first mesh structure based on        an input parameter set to define an operational environment; and    -   generating a set of robot instructions to apply additional        material to the first mesh structure based on the defined        operational environment, the additional material being used for        modifying the first mesh structure in order to provide a second        mesh structure.

In a tenth embodiment, a robot for generating a mesh structure isprovided, comprising the processing unit according to the ninthembodiment.

In an eleventh embodiment, a computer program is provided, comprisinginstructions which, when the program is executed by a computer, causesthe computer to carry out the method according to any one of embodiments8.

In a twelfth embodiment, a mesh structure is disclosed, obtainable bythe method according to embodiment 8.

A thirteenth aspect or embodiment (according to application number EP 20205 632.1) relates to a method for generating mesh data to construct amesh structure to be used in a constructional building process,comprising:

-   -   processing an input geometry object and creating a digital        representation of the input geometry object;    -   structurally evaluating the digital representation of the input        geometry object;    -   determining a structural requirement set; and    -   generating mesh data based on the digital representation of the        input geometry object and the structural requirement set, the        mesh data defining a characteristic of a mesh structure to be        constructed by a robotic fabrication process.

In the thirteenth embodiment, the structural requirement set isdetermined based on the structural evaluation of the digitalrepresentation.

In the thirteenth embodiment, the method may further comprise segmentingthe digital representation of the input geometry object in a pluralityof elements, wherein the mesh data is generated based on the pluralityof elements and the structural requirement set.

In the thirteenth embodiment, the digital representation is segmented inthe plurality of elements based on a size of the mesh structure to beconstructed by the robotic fabrication.

In the thirteenth embodiment, the method may further comprise generatinga set of construction instructions based on the characteristic of themesh structure defined in the mesh data, the set of constructioninstructions being used by a robotic system for the robotic fabricationprocess of the mesh structure.

In the thirteenth embodiment, the characteristic of the mesh structurecomprises a number of nodes in the mesh structure, positions of thenodes in the mesh structure, wire data, topology information of the meshstructure, a type of material used for the mesh structure, a type ofjoining method, and/or a set of joining parameters.

In the thirteenth embodiment, the input geometry object is modelled in adata structure to create the digital representation of the inputgeometry object.

In the thirteenth embodiment, the input geometry object is a mesh objectand/or a non-uniform rational B-spline (Nurbs) surface.

In the thirteenth embodiment, structurally evaluating the digitalrepresentation is based on a structural analysis and/or structural load.

In the thirteenth embodiment, determining the structural requirement setcomprises determining a reinforcement requirement set for the meshstructure to be constructed by the robotic fabrication.

In the thirteenth embodiment, the reinforcement requirement setcomprises an amount of reinforcement, a type of reinforcement, a type ofmaterial used for reinforcement, a reinforcement bar (rebar) spacing,and/or a rebar diameter.

In the thirteenth embodiment, the amount of reinforcement to be placedon a specific position for the mesh structure to be constructed by therobotic fabrication process is calculated based on the input geometryobject and a load case.

In the thirteenth embodiment, the method may further comprise checkingthe generated mesh data for fabrication feasibility and providing achecking result.

In the thirteenth embodiment, checking the generated mesh data forfabrication feasibility comprises checking minimum and maximum spacing,minimum curvature, overlaps, and/or build volume.

In the thirteenth embodiment, if it is determined that fabricationfeasibility is not given, the mesh data is adapted by repeating thesteps of structurally evaluating the digital representation, determiningthe structural requirement set, and generating the mesh data, and/or themesh data is adapted based on the checking result.

In a fourteenth embodiment, a processing unit for generating mesh datato construct a mesh structure to be used in a constructional buildingprocess, configured to perform the steps of:

processing an input geometry object and creating a digitalrepresentation of the input geometry object;

-   -   structurally evaluating the digital representation of the input        geometry object;    -   determining a structural requirement set; and    -   generating mesh data based on the digital representation of the        input geometry object and the structural requirement set, the        mesh data defining a characteristic of a mesh structure to be        constructed by a robotic fabrication process.

In a fifteenth embodiment, an apparatus is provided for generating meshdata to construct a mesh structure to be used in a constructionalbuilding process, the apparatus comprising the processing unit accordingto the fourteenth embodiment.

In a sixteenth embodiment, computer program comprising instructionswhich, when the program is executed by a computer, causes the computerto carry out the method according to any one of embodiments thirteen,mentioned above.

Generally, the term “strand” may be construed as “secondary meshstructure” or as rebar, wire or band material or material to be used inmesh construction.

The term “primary building structure” may be construed as primary meshstructure.

The term “feed wire” may be construed as secondary mesh structure.

The properties, features and advantages of this invention describedabove, as well as the manner they are achieved, become clearer and moreunderstandable in the light of the following description andembodiments, which will be described in more detail in the context ofthe drawings. This following description does not limit the invention onthe contained embodiments. Same components or parts can be labeled withthe same reference signs in different figures. In general, the figuresare not for scale.

It shall be understood that a preferred embodiment of the presentinvention can also be any combination of the dependent claims or aboveembodiments with the respective independent claim.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic representation of an end-effector forconnecting of secondary mesh structure 2 ms to a primary mesh structure1 ms;

FIG. 2 a -FIG. 2 e shows a process for welding the secondary meshstructure to the primary mesh structure in different phases;

FIG. 3 shows the end-effector with its components in more detail;

FIG. 4 is an overview figure of the process for generating a meshstructure according to a preferred embodiment of the present invention;

FIG. 5 is a block diagram of digital components and related data ormessage exchange according to another preferred embodiment;

FIG. 6 shows by way of example two end-effectors for mesh generation;

FIG. 7 is an overview figure, representing different coils for providingthe secondary mesh structure to be used by the robot for generating themesh structure;

FIG. 8 is another perspective of the robotic setting with twoend-effectors and is platforms with two linear actuators;

FIG. 9 is a block diagram of an end-effector tool with two end-effectorsand their respective components according to a preferred embodiment ofthe invention;

FIG. 10 is a flow chart to a computer-implemented method for instructingsteps to be executed on an end-effector;

FIG. 11 is another schematic representation of a robotic process forgenerating the mesh structure;

FIG. 12 is a flow chart, representing functional dependencies;

FIG. 13 shows the end-effector EE when applying the secondary meshstructure onto the primary mesh structure by rolling over.

DETAILED DESCRIPTIONS OF THE FIGURES AND PREFERRED EMBODIMENTS

This following description does not limit the invention on the containedembodiments. Same components or parts can be labeled with the samereference signs in different figures. In general, the figures are notfor scale.

It shall be understood that a preferred embodiment of the presentinvention can also be any combination of the dependent claims or aboveembodiments with the respective independent claim.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

In case, complex wall or ceiling systems needed to be manufactured,usually it is necessary to provide the concrete with a reinforcementstructure. Typically, the reinforcement structure is provided first,like the mesh structure, which may be later filled with concrete. Thepresent invention now relates to the automatic generation of such a meshstructure, in particular a three-dimensional mesh structure for use inconstructional engineering, like for example for building reinforcedconcrete structures. However, the method for generating a mesh structureand us so generated mesh structure may also be applied in othersettings, like for example in furniture construction, in façadeconstruction or the like. Further, it is possible to use the generatedmesh structure without later filling with concrete.

Depending on the complexity of the respective structure to be built,there exist a variety of different static requirements for thegeneration of the mesh structure. Typically, a three-dimensional modelis provided, which represents the static requirements. For example, themodel may require to use different types of wires (for instancedifferent dimensions and/or different material) in different regions ofthe mesh structure to be built. For example, a region with a lot ofcurvatures needs a denser reinforcement and thus a mesh structure beingdenser or comprising mesh elements with a higher diameter. So, thespecifications for different regions in one and the same mesh structuremay vary.

As mentioned above, the process for finally manufacturing the buildingstructure, comprising the reinforcing mesh structure requires severalsteps and is time-consuming. Therefore, the present invention aims at afurther automation of the mesh generation process.

For this purpose, a robotic end-effector tool has been developed. Therobotic end-effector tool (in the following simply abbreviated as tool)may comprise at least one and preferably two end-effectors EE. Theseend-effectors EE are implemented on and/or supported by an articulatedarm, so that the end-effector EE is able to move in 6 degrees offreedom. Thus, preferably, the end-effector and/or the end-effector toolis mobile.

Such an end-effector EE is shown in FIG. 1 . As can be seen, theend-effector EE comprises a head, which is depicted schematically inFIG. 1 . The end-effector EE is configured to connect a secondary meshstructure 2 ms, which preferably may be provided as wire, to a primarymesh structure 1 ms. The primary mesh structure 1 ms may bepre-fabricated and is typically provided as two- or three-dimensionalmesh wire structure, as can be seen in FIG. 1 .

The end-effector EE may comprise different modules for via processing,in particular:

-   -   A welding unit W, which is configured for welding wire. The        welding unit W may be used for welding-off wire from the mesh        structure, typically from the primary mesh structure 1 ms. The        welding unit W may also be configured to be used to weld the        secondary mesh structure 2 ms onto the primary mesh structure 1        ms. In a preferred embodiment, the welding unit W is the        resistance or contact welding unit.    -   A bending unit B, which is configured for bending wire. The        bending unit B is typically used for bending the secondary mesh        structure 2 ms according to the shape of the primary mesh        structure 1 ms. In a preferred embodiment the bending unit B may        be provided as anode of the welding unit W. So, one part of the        welding unit W additionally serves as bending unit B as well.        This is reflected in FIG. 9 with the bracket around the welding        unit W and the bending unit B.    -   A set of sensors S, comprising at least one sensor for detecting        a contact force which is applied by end-effector EE onto the        primary mesh structure 1 ms. Preferably, one contact force        sensor is provided at the head of the end-effector EE.        Optionally, further sensors may be provided, including terminal        sensors, noise sensors, optical sensors and/or other sensors for        detecting signals during rolling over the primary mesh structure        1 ms.    -   The rebar threader R for providing the secondary mesh structure        2 ms (for instance in the form of a rebar strand) from our        supply unit, like a coil. The rebar threader R is a hollow        structure with an inlet and an outlet for guiding the secondary        mesh structure 2 ms (or rebar) from the supply of oil to the        rolling anode.    -   Optionally, the end-effector EE may comprise a cutter C, which        is configured for cutting wire, and in particular for cutting        the secondary mesh structure 2 ms after completion of the        sequence of welding processes.

In a preferred embodiment, the anode of the welding unit is configuredas bending unit, so that no separate component is necessary for bending.In this case the bending unit B is implemented or integrated in thewelding unit W.

FIG. 9 schematically shows the end-effector tool with two end-effectorsEE1, EE2, each comprising the welding unit W, the bending unit B, acutter C and the set of sensors S with the contact force sensors.Preferably, the welding unit W is a resistance welding unit andcomprises an anode which is preferably implemented as rotating roll, ascan be seen in FIG. 2 a-d and/or might be made from copper. The anode inthe form of the rotating roll is configured to be rolled over theprimary mesh structure 1 ms with the secondary mesh structure 2 ms. Thewelding unit W further comprises a cathode which preferably isimplemented as dog or carrier.

The carrier may be provided as rectangular unit and may be attached on asupport member at the end-effector EE, so that the cathode may swivel orpivot around an axis, extending perpendicular to the surface of theprimary mesh structure 1 ms. Generally, it is key that the cathodetouches the respective primary structure that is welded to the secondarystructure before sending the weld signal. As can be seen in FIG. 2 , thecathode is supported at the end-effector EE to engage with the primarymesh structure 1 ms when the end-effector EE is rolled over the primarymesh structure 1 ms. The cathode is forced to swivel around theabove-mentioned axis when the end-effector EE is moved translatory in aY- and/or Z axis. If the end-effector EE is moved from one wire element(element of the primary mesh structure 1 ms, over which the end-effectorEE with the secondary mesh structure 2 ms is rolled) to the next wireelement of the primary mesh structure 1 ms, the cathode is forced to hopor jump to the next element. Preferably, the cathode is spring-mountedon a support member of the end-effector EE.

As represented in FIG. 9 with dotted lines, the processor P may beimplemented on the end-effector tool or may be associated thereto.Alternatively, or in addition, the processor P may also be implementedon each or on selected end-effectors locally. Both, of theabove-mentioned alternatives may be combined.

Further, the end-effector EE may comprise a rebar threader R forforwarding the rebar or wire of the secondary mesh structure 2 ms to theend-effector EE from a coil.

FIGS. 2 a to 2 e shows a top view of the end-effector EE during rollingover the primary mesh structure 1 ms for welding the secondary meshstructure 2 ms at pre-configured positions. Typically, the weldingpositions are defined by the three-dimensional model. A welding positionis defined by a wire crossing between a wire of the primary meshstructure 1 ms and the wire of the secondary mesh structure 2 ms.Depending on the model, not every wire of the primary mesh structure 1ms needs to be subject for the welding process. With other words it ispossible that only a selection of wire elements of the primary meshstructure 1 ms are subject to the welding process. In FIG. 2 a-e thefollowing different states in the course of rolling-over can be seen:

a) End-effector EE approaching welding position;b) Cathode touching primary structure 1 ms;c) Welding by means of the welding unit W;d) Welding finished;e) Cathode jumping from one primary structure element to the next whilethe robot is moving along the desired trajectory.

FIG. 3 shows the head of the end-effector EE in another perspective. Theend-effector EE is provided with a transformer, the cuboid component inFIG. 3 , for providing the appropriate voltage. The cathode and theanode are electrically connected for voltage supply by a cathode cableand an anode cable. As already described above, the cathode ispreferably provided as rectangular bar, which is spring-mounted androtatable around an axis being perpendicular to the movement directionof the end-effector EE and/or usually parallel to the (e.g., verticallyextending) elements of the primary mesh structure 1 ms. In this respectit has to be noted, that the rotation axis for the spring-mountedcathode has a lateral offset to the surface of the primary meshstructure 1 ms.

In a preferred embodiment and as shown in FIG. 3 , the anode is providedas rolling bending unit B. Thus, the anode has two functions:

-   -   1. for welding, besides the cathode, as part of the welding unit        W and    -   2. for bending; the anode serves as a bending unit B for bending        the secondary mesh structure 2 ms in the direction, being        parallel to the surface of the primary mesh structure 1 ms along        with the movement of the end-effector EE rolling over the        primary mesh structure. As can be seen in FIG. 3 , the anode may        be provided as pulley or roll, being rotatable around a rotation        axis, being perpendicular the movement direction the effector EE        and/or parallel to the surface of the primary mesh structure 1        ms.

The end-effector EE itself is movable in 6DOF of freedom. Further, theend-effector EE comprises the rebar threader R for providing thesecondary mesh structure 2 ms in the form of wire or rebar as mentionedabove (see FIG. 9 ).

FIG. 4 shows the whole process for generating the mesh structure in aschematic overview figure. In step 1 a 3D mesh model is generated to beprovided in a digital form to several computing entities and processors.A two-dimensional part of the primary mesh structure 1 ms is fabricatedin step 2 by means of using robots (step 4) which are configured forbending the appropriate wire into a form which is defined by the 3D meshmodel. A set of such two-dimensional parts of the primary mesh structure1 ms are placed (and non-permanently attached, for instance by weldingconnections) on a platform (step 5) in order to generate the primarymesh structure 1 ms, which is a three-dimensional mesh structure. Thisprimary mesh structure 1 ms e.g., with curvatures in different axesserves as basis for generating the mesh structure with a methodaccording to the present invention. The primary mesh structure 1 ms isprocessed by the mobile robotic end-effector tool with an end-effectorEE for welding two different types of rebar/wires or secondary meshstructures 2 ms, stocked on two different coils, as can be seen in FIG.4 on the right-hand side onto the primary mesh structure 1 ms. Therobotic end-effector EE is provided on an articulated robotic arm, whichitself is articulated attached on a platform. The platform may be movedby linear driver motors. Thus, the platform with the end-effector EE maybe moved in lateral direction and mainly in parallel to the surface ofthe primary mesh structure 1 ms. The end-effector EE is instructed toroll over the primary mesh structure 1 ms in order to weld the secondarymesh structure 2 ms at configurable welding positions. Typically, therolling over process is reiterated in different heights (Z axisdirection), depending on the static requirements. Usually, the secondarymesh structure 2 ms may be welded in a configurable angle onto elementsof the primary mesh structure 1 ms. For some applications, a 90° anglebetween the secondary mesh structure 2 ms and the primary mesh structure1 ms is favorable. After having completed all roll spot weldings with aplurality of different sequences (preferably a plurality of rows orlines of the secondary mesh structure), the final mesh is generated, ascan be seen in FIG. 4 on the right-hand side.

FIG. 5 shows the general data exchange. A processor P (also referred toherein as processing unit) serves to calculate control instructions forcontrol of the robotic end-effector tool with the at least oneend-effector EE. Further, the processor P serves to receive the digitalthree-dimensional model, representing requirements for the meshstructure to be built. The requirements, inter alia, are defining thetype of secondary mesh structure 2 ms (for instance rebar strands frommetal or in another material, in a certain diameter, and/or with certainphysical—chemical properties etc.). The processor may be configured togenerate:

-   -   1. static control instructions, which are fix and static for one        process of rolling over (the secondary mesh structure onto the        primary mesh structure). The static control instructions may in        a preferred embodiment be solely calculated on the basis of the        3D model and may e.g., take into account material properties for        defining welding parameters like the welding current, voltage        etc.    -   2. Dynamic control instructions, which are variable or may        change over the process of rolling over. The dynamic control        instructions are preferably calculated in response to the        measured contact force and/or the target contact force. The        target contact force may be determined by the 3D model. The        dynamic control instructions may preferably relate to the        positioning instructions for the end-effector EE (target        trajectory).

Based on the information in the model, the processor P calculatescontrol instructions with a set of control signals for instructing theset of end-effectors EE1, EE2, EE3. The control signals comprisetrajectory signals, defining the desired trajectory, the end-effector EEis required to move along the primary mesh structure 1 ms. Usually, thetrajectory signals are predefined by the digital three-dimensional modelonly approximately or roughly, because the primary mesh structure iscompliant and may go to side or move back/side or away, if a force isapplied to it in direction of the normal onto the surface of the primarymesh structure. Such a force is applied inevitably when the end-effectoris rolled over the primary mesh structure, which prompts the primarymesh structure—at least at that position—to change its position in Xdirection (bounce back a little). Therefore (because of the movingtarget namely the primary mesh structure) the trajectory needs to beadapted according to the instantaneous and dynamically measured contactforce at that point. Further, the force is physically dependent of theposition of the end-effector EE. For example, if the end-effector EE ismoved along a desired trajectory over the primary mesh structure and atarget force Ft needs to be applied at a particular position, due to theflexibility of the primary mesh structure (bounce backwards) theactually measured force Fa (measured at that position) might be lowerthan the target force Ft. Then, the end-effector EE may be controlled toreposition (offset in X direction towards the primary mesh structure) sothat the target force Ft may be reached. If the actually measured forceFa is too high, the control signals may instruct the end-effector EE toreposition (away from the primary mesh structure) so that the targetforce Ft may be reached.

The set of control signals further comprises signals, defining thewelding process and may be referred to as welding control signals. Thewelding control signals serve and are adapted to define the weldingprocess of the welding unit W of the respective end-effector EE. Thewelding control signals may comprise: the welding current, the weldingvoltage, the welding power, the welding energy. Typically, theabove-mentioned control signals are kept constant, whereas the contactforce is controlled dynamically. A control of the electrical variablesand, in particular, a control of the contact force is important forensuring stability of the mesh and its welding connections. The weldingcontrol signals are preferably optimized in view of material propertiesand parameters (e.g., mesh diameter etc.). The static welding controlsignals (e.g., except the contact force) may be pre-set and maypreferably be kept constant during rolling over the primary meshstructure 1 ms (by the end-effector EE).

The contact force is processed in two different instances: as measuredcontact force and as instructed contact force. On the one hand, thecontact force is measured by sensors at the end-effector EEcontinuously. On the other hand, the contact force is instructed by aprocessor P to be applied when performing the welding spots. Themeasured contact force may differ from the instructed contact force fora number of reasons. Mainly material deformation and/or materialtwisting and/or distortions and/or other forms of re-positionings of theprimary mesh structure may be the reason for the deviations. With this,a closed control loop for controlling the welding parameters for thewelding process may be provided.

One major advantage of the present invention is, that the contact forceis dynamically and/or adaptively controlled in a closed loop control.For this purpose, the end-effector EE comprises sensors for measuringthe contact force. Generally, the contact force may be influenced by avariety of different parameters, including static parameters, likegeometric parameters of the primary mesh structure 1 ms, and dynamicparameters, like e.g., additional forces being applied to the primarymesh structure 1 ms at that timepoint (for instance from anotherend-effector EE, working in parallel on the primary mesh structure 1 msand/or other technical parameters). Thus, the measured and instructedcontact force may vary from position to position over the primary meshstructure or may vary over time. Further, the correct application of thecontact force is essential for the quality of the welding process andneeds to be controlled. If, on the one hand, the contact force isapplied too low, a sufficient welding connection between the respectivewires cannot be assured and quality may be impaired. If, on the otherhand, too much contact force is applied, the welding process takes toolong and the structure of the respective wires may be impaired.Therefore, a correct and appropriate application of the contact force isessential. Further, the contact force to be applied is dependent on thephysical parameters of the respective two rebars (wires of the first andsecondary mesh structure) to be connected, like for example the diameterof the rebars. The goal of the control loop is to keep the contact forceconstant per element, by adjusting the position of the end-effector. Adifferent target force might be defined if the material and/or diameterchanges.

The process of contact welding (resistance welding) may preferably becontrolled such as to provide a constant and continuous contact forceand/or also other welding parameters over time and in particular duringrolling over the primary mesh structure. In contrast to usual processcontrol in resistance spot welding, which has the task ofcontrolling/guiding the welding process in the case of changinginfluencing variables in such a way that sufficient joint quality of theresulting weld spot is ensured the present suggestion, presented hereinserves to adapt the trajectory and/or position over time/movement of theend-effector for indirectly influencing and controlling at least onewelding parameter, namely the contact force.

According to a preferred embodiment of the invention, the contact force,in particular the instructed contact force, is controlled adaptively andin response to the measured contact force during the process of rollingover the primary mesh structure 1 ms. For example, a first secondarymesh structure needs to be applied with a different contact force than asecond secondary mesh structure. having e.g., another welding resistanceand/or for which another welding voltage and/or current have beenmeasured.

FIG. 6 shows an end-effector tool, comprising two separate end-effectorsEE, working from opposite sides on the same primary mesh structure 1 ms.In a preferred embodiment, the two end-effectors EE are controlled incommon so that they are positioned at corresponding positions onopposite sides of the primary mesh structure 1 ms and thus have acorresponding position in the Y- and Z-axis for force balancing. As canbe seen the secondary mesh structures 2 ms are provided on two differentcoils. Each end-effector EE is positioned on a separate platform. Eachplatform is movable by drive motors. Preferably the platform is movablein one axis (laterally), namely in the Y-axis. In addition, theend-effector EE is provided at an articulated arm and is thus mobile in6 DOF of freedom to operate on the primary mesh structure 1 ms.

FIGS. 7 and 8 show a similar setting as FIG. 6 in another perspectivewith the two coils for providing the secondary mesh structure 2 ms beingprovided below or besides the platforms.

FIG. 10 shows in an abstract representation of the process of rollingover the primary mesh structure 1 ms for roll spot welding. The start ofthe actions of the end-effector EE may be initiated upon an initiationsignal, which may be provided on a user interface, e.g., associated to aserver computer or to the processor P. The process may be executed in aprocessor P, which may be implemented on different computing entities.The processor P is configured for control of the end-effector EE. Theprocessor may be implemented on the end-effector EE or a relatedcomputing entity, being in data exchange. In step S1 the welding may beinstructed by respective control signals. In step S2 the measurement maybe instructed by respective control signals. Alternatively, themeasurement is executed continuously and the measured signals areprocessed upon instruction (by the processor P). The steps are to beunderstood as action to be performed during rolling over—represented inFIG. 10 by reference numeral S4 —; they may be executed in parallel orin another sequence or interleaved. During the process of rolling over,roll spot welding is performed. In parallel, the end-effector EE and inparticular the welding process of the welding unit W of the end-effectorEE is controlled dynamically, shown with S3. The action roll-over S4 andcontrol S3 are executed in parallel.

FIG. 11 shows a manufacturing pipeline or robotic process for generatingthe mesh structure from left to right. The secondary mesh structure 2 ms(wire), represented on the left downward section in FIG. 11 may be usedfor generating the first mesh structure 1 ms (2D part) by bending robotsin a preceding step. The so generated first mesh structure 1 ms (2Dpart) may be fabricated in sequence, one after the other. In a nextprocess step of the automation pipeline shown in FIG. 11 , a set of such2D-parts are the fixed on a platform and are referred to herein as firstmesh structure 1 ms. These separate first mesh structures 1 ms need tobe connected to each other to generate the (final mesh structure) byanother secondary mesh structure (here: two different wires), shown onthe right of FIG. 11 . Typically, another instance or element of thesecondary mesh structure is used for generating the first mesh structure(as shown on the left) as the secondary mesh structure which is used toconnect the set of first mesh structures (to provide the final meshstructure), shown in this figure on the right.

FIG. 12 shows functional dependencies of involved parameters accordingto a preferred embodiment of the present invention. A digital blueprintmay be stored in a storage and indicates the target or desired force aswell es the target or desired trajectory for movement of theend-effector EE, to be applied when welding the secondary mesh structure2 ms to the primary mesh structure 1 ms. Preferably, two separatecontrollers are used: one controller for controlling the contact forceof the end-effector EE and one controller for controlling theposition/movement of the same. At the robotic arm of the end-effectorEE, in particular at the head of the same, a contact force sensor isattached, which is configured for continuously measuring the contactforce or pressure, which is provided to the processor P (not shown) tocompare the measured contact force with the desired contact force and tocalculate in response to this comparison an adapted trajectory for theposition controller.

FIG. 13 shows the end-effector EE while rolling over the primary meshstructure 1 ms. Here, the rectangular cathode is referenced with numeralC and the rolling anode with numeral A and the rebar threader withnumeral R which provides the secondary mesh structure 2 ms to therobotic end-effector EE. The cathode C engages with the primary meshstructure 1 ms as it hops from wire element to wire element of theprimary mesh structure 1 ms while the end-effector EE with its anode Ais rolling over the primary mesh structure 1 ms. As indicated in FIG. 13, two of such end-effectors EE may be used from opposite sides, workingin parallel on the primary mesh structure 1 ms.

Wherever not already described explicitly, individual embodiments, ortheir individual aspects and features, described in relation to thedrawings can be combined or exchanged with one another without limitingor widening the scope of the described invention, whenever such acombination or exchange is meaningful and in the sense of thisinvention. Advantages which are described with respect to a particularembodiment of present invention or with respect to a particular figureare, wherever applicable, also advantages of other embodiments of thepresent invention.

1. Method for generating a mesh structure for use in constructionalengineering, in particular for use in reinforcement systems, comprisingthe method steps of: Providing a primary mesh structure (1 ms), Using arobotic end-effector tool with at least one end-effector (EE), beingmovable in six degrees of freedom for applying an endless secondary meshstructure (2 ms) to the provided primary mesh structure (1 ms)continuously by roll spot welding; and during rolling over (S4) theprimary mesh structure (1 ms) for roll spot welding: instructing (S1) awelding unit (W), in particular a resistance welding unit, to initiate awelding process in a sequence of interrupted welding processes forwelding the secondary mesh structure (2 ms) to the primary meshstructure (1 ms) at pre-defined connection positions to generate crossweldings; instructing (S2) a set of sensors (S) to measure a contactforce at the robotic end-effector (EE), being applied to the primarymesh structure (1 ms) during rolling over (S4) the primary meshstructure (1 ms); controlling (S3) the robotic end-effector in real-timewith control signals, generated by a processor (P), wherein the controlsignals are generated at least in part in response to the measuredcontact force.
 2. Method according to claim 1, wherein the welding unit(W) is a resistance welding unit or a gas metal arc welding unit or atying gun for providing a tying connection.
 3. Method according to anyof the preceding claims, wherein the control signals comprise firstcontrol signals, being dynamic and indicating a trajectory for movementof the end-effector (EE) and second control signals, indicating weldingparameters for executing the welding process in the sequence ofinterrupted welding processes and/or wherein the second control signalsare static.
 4. Method according to the directly preceding claim, whereinthe first control signals are determined on the basis of the measuredcontact force and/or wherein the second control signals are determinedon the basis of a 3D mesh model.
 5. Method according to any of thepreceding claims, wherein the secondary mesh structure (2 ms) is orcomprises a strand of continuous mesh material, in particular mesh wire.6. Method according to any of the preceding claims, wherein thesecondary mesh structure (2 ms) is bent by means of the end-effector andin particular by means of an anode of the welding unit (W) and/orwherein the secondary mesh structure (2 ms) is bent during rolling overthe primary mesh structure (1 ms), in particular according to acurvature of the first mesh structure (1 ms).
 7. Method according to anyof the preceding claims, wherein the secondary mesh structure (2 ms) isnot cut to length while rolling over the primary mesh structure (1 ms)and/or wherein the secondary mesh structure (2 ms) is not cut to lengthbefore an outer side of the primary mesh structure (1 ms) has beenreached after the process of rolling over the primary mesh structure (1ms) has started.
 8. Method according to any of the preceding claims,wherein the sequence of interrupted welding processes is applied withone and the same endless secondary mesh structure (2 ms).
 9. Methodaccording to any of the preceding claims, wherein the roboticend-effector tool comprises at least two separate end-effectors (EE) attwo different robotic arms, wherein the two separate end-effectors areused in parallel for applying different items of the secondary meshstructure (2 ms) to the primary mesh structure (1 ms), in particular onthe same height and/or in the same longitudinal extension in the Y-axisfrom opposite sides.
 10. Method according to any of the precedingclaims, wherein the contact force is measured by means of a forcemeasurement sensor, which is attached at a head of the roboticend-effector (EE), in particular in an area where the contact force isapplied.
 11. Method according to any of the preceding claims, whereinduring the sequence of interrupted welding processes, the secondary meshstructure (2 ms) remains in endless form and is not cut.
 12. Methodaccording to any of the preceding claims, wherein the secondary meshstructure (2 ms) is welded to the primary mesh structure (1 ms)horizontally or vertically or in an angle between 0° and 90° withrespect to a direction of an element of the primary mesh structure (1ms).
 13. Method according to any of the preceding claims, wherein the atleast one end-effector (EE) is adapted: to weld the secondary meshstructure (2 ms) onto the primary mesh structure (1 ms); to weldelements off the primary mesh structure (1 ms); to move and inparticular to roll over the primary mesh structure (1 ms), bytranslatory and/or rotational movements, depending on the curvature ofthe primary mesh structure (1 ms); to bend the secondary mesh structure(2 ms), in particular in case the primary mesh structure (1 ms) is notplanar, and/or to cut the secondary mesh structure (2 ms) aftercompletion of the sequence of interrupted welding processes.
 14. Methodaccording to any of the preceding claims, wherein the at least oneend-effector (EE) comprises an anode and a cathode, wherein the anode isprovided as rotating roller and the cathode is provided as rotatingcarrier, which hops or skips to a respective next element of the primarymesh structure (1 ms).
 15. Method according to any of the precedingclaims, wherein the at least one robotic end-effector (EE) is placed ona mobile platform, and/or wherein the mobile platform is transferable bya linear actuator for linear movement, in particular parallel to a planeof the primary mesh structure (1 ms).
 16. Method according to any of thepreceding claims, wherein the at least one robotic end-effector (EE) ismoved along a trajectory over the primary mesh structure (1 ms)according to control instructions which are calculated on the basis of adigital 3D-model.
 17. A robotic end-effector tool for generating a meshstructure for use in constructional engineering, in particular for usein reinforcement systems, which is configured to be used in a methodaccording to any of the preceding method claims, comprising: at leastone robotic end-effector (EE), being movable in six degrees of freedomfor applying an endless secondary mesh structure (2 ms) to the providedprimary mesh structure (1 ms) continuously by roll spot welding, whereinthe at least one robotic end-effector (EE) further comprises: a weldingunit (W), in particular a resistance welding unit, configured forwelding the secondary mesh structure (2 ms) to the primary meshstructure (1 ms) at pre-defined connection positions to generatecross-wire connections; contact force sensors, configured for measuringthe contact force of the robotic end-effector (EE), being applied to theprimary mesh structure (1 ms) during rolling over the primary meshstructure (1 ms); a processor (P) for closed loop control of the atleast one robotic end-effector (EE) by means of control signals, whereinthe control signals are generated at least in part in response to themeasured contact force.
 18. The robotic end-effector tool according tothe directly preceding claim, wherein the welding unit (W) comprises ananode and a cathode, and wherein the anode is configured for bending thesecondary mesh structure (2 ms) during rolling over the primary meshstructure (1 ms).
 19. A computer program comprising a computer programcode, the computer program code when executed by a processor causing arobotic end-effector tool according to the directly preceding claim toperform the steps of the method of any of the preceding method claims,when the robotic end-effector (EE) is provided with a primary meshstructure (1 ms) and in case an initiation signal is provided.